The main opposition party the Muslim Brotherhood says the poll was "rigged and invalid" The US has said it is "dismayed by reports of election-day interference and intimidation by security forces" in Egypt, which it counts as a key ally.
Voters in Egypt went to the polls on Sunday to elect a new parliament. A result is expected later, with a second round of run-off voting set for Sunday.
Opposition parties allege widespread bullying and ballot-stuffing. The main opposition Muslim Brotherhood says it failed to win a single seat outright.
The government says the poll was fair.
ThugsEgyptian media have carried images and testimonies of mass faked ballots and thugs intimidating voters at polling stations, and protests erupted around Egypt following Sunday's voting.
"We are disappointed by reports in the pre-election period of disruption of campaign activities of opposition candidates and arrests of their supporters," said US state department spokesman Philip Crowley.
"We are also dismayed by reports of election-day interference and intimidation by security forces," he added.
The Muslim Brotherhood denounced the vote as "rigged and invalid".
The party is barred from taking part in Egyptian elections, so its candidates stand as independents.
They currently hold 88 seats in parliament - nearly a fifth of the assembly's 508 seats. The Brotherhood now says none of its 130 candidates won an outright victory - though one report indicates that one woman has been elected into a newly formed women's quota of deputies.
Twenty-seven candidates will go through to Sunday's run-offs, AP news agency reported, along with a handful of the 222 candidates who ran for the liberal New al-Wafd party.
Reports say the ruling NDP party has won 170 seats outright.
Call for investigationThe government violated a "presidential promise" to hold free and fair elections, the New al-Wafd party charged on the front page of its party newspaper.
It called on the government's election commission to postpone the announcement of the official results until it had investigated claims of voting violations.
The results of the poll could leave the ruling party of President Hosni Mubarak with an embarrassingly large majority in the new parliament, says the BBC's correspondent in Cairo, Jon Leyne.
It could further undermining the credibility of a process in which few Egyptians even bother to participate.
Some 42 million voters were eligible to cast their ballots - but a coalition of human rights groups suggests turnout was only 10-15%, reported AP.
The new parliament will have 518 members, 508 of whom will be elected and 10 of whom will be appointed by presidential decree.
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